Saw mills typically cut lumber, such as 2.times.4's and the like, on what might be described as a conveyor belt operation. The finished products arrive at the end of the conveyor belt and are stacked horizontally using forks which lay a tier of lumber onto a stack of such lumber. The stack of lumber are stacked on a hoist which lowers the stack by the depth of one tier every time a new tier is added. In this way the elevation of the forks does not have to be changed in order to add a new tier to the stack. For example, if the finished products are 2.times.4 then the hoist will lower the stack by 2 inches every time a new tier is added. The forks will typically deliver ten 2.times.4's and deposit them horizontally as a new tier onto the stack.
Stacks of lumber, such as 2.times.4's, must be stabilized by using what are called "binders". Typically binders are wooden lathing which, after a certain number of tiers have been placed onto the stack, are laid transversely across the stack before the next tier of planks is added. The lathing will typically be aligned at right angles to the lumber and laid across a tier at approximately 5 foot intervals. In the case of 2.times.4's, binders are typically placed onto the stack after every seven tiers.
In the prior art, many machines have been devised for placing laths and what are commonly referred to as "stickers", onto stacks of lumber. Stickers are placed between individual tiers of green, that is, newly cut, lumber so as to allow drying of the lumber. Typically sticker placing machines incorporate elaborate and bulky conveyor mechanisms for feeding stickers into pockets, chutes or cam-like feeding devices so that stickers may be transferred to, and laid transversely across, a stack of lumber before the next layer of lumber is added to the stack. A frequent problem recited in the prior art in handling of such stickers is that typically the stickers will not be of uniform thickness and will be warped or otherwise deformed thereby making automatic handling difficult.
Attempts have been made in the prior art to overcome such difficulties, notably by Whiddon, U.S. Pat. No. 4,878,803 issued 7 Nov. 1989, who disclosed a system mounted to a translatable carriage whereby finger-like gripping means would pick up the stickers individually from a sticker conveyor and release them onto the lumber stack once the translatable carriage moved the sticks from the sticker conveyor to a position over the lumber stack.
A system employing vacuum means for picking up lumber and stickers has been previously disclosed by Icard, U.S. Pat. No. 3,737,034 issued 5 Jun., 1973. Icard teaches using elongated vacuum conveyor belts for unstacking tiers of lumber from stacks of lumber. The mechanism is adapted to pick up an entire tier of lumber, and any associated stickers lying loose on top of the tier, by applying a vacuum to a spaced parallel array of conveyor belts. The belts are only adapted to adhere to the lumber itself and not the stickers.
A system employing a rotary machine for placing stickers has been previously disclosed by Kennison, U.S. Pat. No. 4,264,253 issued 28 Apr., 1981. Kennison teaches using a notched rotary wheel for receiving stickers from a vertical gravity feed stack. Stickers are received in the wheel notches and deposited onto a lumber stack positioned beneath the wheel. Stickers are deposited as the wheel is rotated causing the stickers to fall from the notches. It can be seen however that the mechanism will jam if warped stickers or stickers which are uneven or too thick or too thin are fed from the gravity feed stack into the wheel notches.
The present invention addresses the difficulties in systematically placing lathing or stickers onto a lumber stack so as not to interfere with the efficient delivery of finished planks onto the stack. The present invention is a delivery system for placing laths or stickers which, because of its simplicity, is inherently reliable, and is sufficiently compact so as not to interfere with the operation of the mill.
Hereinafter I will refer to laths, stickers or like substantially flat-sided members collectively as laths or lathing.